Method and apparatus for transmitting and receiving beamforming matrix

ABSTRACT

The present disclosure provides a method and apparatus for transmitting the beamforming matrix. The method includes calculating the maximum value m v (k) of the real part and imaginary part of the elements in subcarrier&#39;s beamforming matrix; carrying out a M bits quantization to m v (k) and obtaining the quantization amplitude M v (k), calculating the linear part M v   lin (k) of M v (k); carrying out a respectively N b  bits quantization to the real part and imaginary part of every element in V(k) by M v   lin (k), and obtaining the quantized beamforming matrix V q (k); N b  is positive integer; transmitting said quantization amplitude M v (k) and said quantized beamforming matrix V q (k).

CROSS-REFERENCE TO RELATED APPLICATION Related Applications

This application claims the benefit of Chinese patent application No.201210025585.3 filed on Feb. 6, 2012 and titled “METHOD AND APPARATUSFOR TRANSMITTING AND RECEIVING BEAMFORMING MATRIX”, which isincorporated herein by reference in its entirety.

This application claims the benefit of Chinese patent application No.201210052998.0 filed on Mar. 2, 2012 and titled “METHOD AND APPARATUSFOR TRANSMITTING AND RECEIVING BEAMFORMING MATRIX”, which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to the field of wireless communications,particularly relates to a method and apparatus for a quantized feedbackof the beamforming matrix.

BACKGROUND OF THE INVENTION

In MIMO system, the access point and the user site adopt the mode ofspatial multiplexing and employ multiple antennas to obtain higher rate.Comparing to the general spatial multiplexing method, an enhancedtechnique is that the user site feeds back channel information to theaccess point, the access point uses certain pre-coding technique basedon the obtained channel information, thereby improves the transmissionperformance.

The MIMO system obtains the channel information in several ways. IEEE802.11n proposed a quantitative feedback beamforming matrix solution,the access point initiates a feedback request, the user site feeds backquantized beamforming matrix of the subcarriers on MIMO channel (alsoknown as v matrix), the access point thus calculates the pre-codingmatrix Q_(k).

For ease of describing the quantized feedback process of the V matrix,hereinafter a user site may be referred to as a transmitter, and theaccess point may be referred to as a receiver. The specific method ofquantized feedback is shown in FIG. 1.

Step S101: the transmitter calculates the maximum value of the real partand imaginary part of the elements in subcarrier's beamforming matrix:

$\begin{matrix}{{{m_{v}(k)} = {\max\begin{Bmatrix}{{\max\{ {{{Re}( {v_{({m,l})}(k)} )}}_{{m = 1},{l = 1}}^{{m = N_{r}},{l = N_{c}}} \}},} \\{\max\{ {{{Im}( {v_{({m,l})}(k)} )}}_{{m = 1},{l = 1}}^{{m = N_{r}},{l = N_{c}}} \}}\end{Bmatrix}}};} & (1)\end{matrix}$wherein v_((m,l))(k) represents the elements in v(k), Re(v_((m,l))(k))represents the real part of v_((m,l))(k), Im(v_((m,l))(k)) representsthe imaginary part of v_((m,l))(k); m is the row position reference, lis the column position reference, N_(r) is the maximum row number, N_(c)is the maximum column number, 1≦m≦N_(r), 1≦l≦N_(c), N_(r)≧1, N_(c)≧1, m,l, N_(r) and N_(c) are all positive integer, k is the subcarrier'sposition reference, which may be a serial number.

Step S102: said transmitter carries out a 3 bits quantization to therelative value

$\frac{\max\{ {m_{v}(z)} \}_{z = {- N_{SR}}}^{z = N_{SR}}}{m_{v}(k)}$of m_(v)(k), to obtain the quantized result M_(v)(k):

$\begin{matrix}{{{M_{v}(k)} = {\min\{ {7,\lfloor {20\;{\log_{10}}^{(\frac{\max{\{{m_{v}{(z)}}\}}_{z = {- N_{SR}}}^{z = N_{SR}}}{M_{v}{(k)}})}} \rfloor} \}}};} & (2)\end{matrix}$wherein

max {m_(v)(z)}_(z = −N_(SR))^(z = N_(SR))is the maximum amplitude value Alpha, └x┘ represents the maximum integernot exceeding x, NSR is the subscript of the maximum data subcarrier.

Step S103: said transmitter calculates the linear part M_(v) ^(lin)(k)of M_(v)(k):

$\begin{matrix}{{M_{v}^{lin}(k)} = {\frac{\max\{ {m_{v}(z)} \}_{z = {- N_{SR}}}^{z = N_{SR}}}{10^{{M_{v}{(k)}}/20}}.}} & (3)\end{matrix}$

Step S104: said transmitter carries out respectively Nb bitsquantization to the real part and the imaginary part of every element inmatrix V(k):

$\begin{matrix}{v_{({m,l})}^{q{(R)}} = {{round}( {\frac{{Re}( {v_{({m,l})}(k)} )}{M_{v}^{lin}(k)}( {2^{N_{b} - 1} - 1} )} )}} & (4) \\{v_{({m,l})}^{q{(I)}} = {{{round}( {\frac{{Im}( {v_{({m,l})}(k)} )}{M_{v}^{lin}(k)}( {2^{N_{b} - 1} - 1} )} )}.}} & (5)\end{matrix}$

Step S105: said transmitter feeds back Alpha, M_(v)(k) and the quantizedbeamforming matrix V^(q)(k) to the receiver.

Step S106: said receiver receives Alpha, M_(v)(k) and V^(q)(k).

Step S107: said receiver calculates the linear value according toM_(v)(k):r(k)=10^(M) ^(v) ^((k)/20)  (6).

Step S108: said receiver carries out a zooming of the real partv_((m,l)) ^(q(R))(k) and the imaginary part v_((m,l)) ^(q(l))(k) of theelements v_((m,l)) ^(q)(k) in matrix V^(q)(k), to recover thebeamforming matrix:

$\begin{matrix}{{{{Re}\{ {{\overset{\sim}{v}}_{({m,l})}(k)} \}} = \frac{\max\{ {m_{v}(z)} \}_{z = {- N_{SR}}}^{z = N_{SR}}{v_{({m,l})}^{q{(R)}}(k)}}{{r(k)}( {2^{N_{b} - 1} - 1} )}}{{{Im}\{ {{\overset{\sim}{v}}_{({m,l})}(k)} \}} = {\frac{\max\{ {m_{v}(z)} \}_{z = {- N_{SR}}}^{z = N_{SR}}{v_{({m,l})}^{q{(I)}}(k)}}{{r(k)}( {2^{N_{b} - 1} - 1} )}.}}} & (7)\end{matrix}$

According to the receiver's decoding process (Equation 7) of thequantized v matrix, the receiver gets that, the feedback overhead neededin the v matrix quantization feedback is the sum of the bit number ofAlpha, M_(v)(k) and v^(q)(k): N_(Alpha)+3+2×N_(b)×N_(r)×N_(c)

SUMMARY OF THE INVENTION

The technical problem to be solved in the present disclosure is, toprovide a method and apparatus for transmitting and receivingbeamforming matrix, and intend to provide a new beamforming matrixquantization feedback scheme. Embodiments consistent with the presentdisclosure ensure the performance of quantitative feedback and reducethe complexity and feedback overhead.

One aspect of the present disclosure provides a method for transmittingthe beamforming matrix, comprising: calculating the maximum valuem_(v)(k) of the real part and imaginary part of the elements insubcarrier's beamforming matrix; carrying out a M bits quantization tom_(v)(k) and obtaining the quantization amplitude M_(v)(k), M ispositive integer; calculating the linear part M_(v) ^(lin)(k) ofM_(v)(k); carrying out a respectively N_(b) bits quantization to thereal part and imaginary part of every element in V(k) by M_(v)^(lin)(k), and obtaining the quantized beamforming matrix V^(q)(k);N_(b) is positive integer; and transmitting said quantization amplitudeM_(v)(k) and said quantized beamforming matrix V^(q)(k).

Another aspect of the present disclosure provides a method for receivingbeamforming matrix, comprising: receiving the quantized subcarrier'sbeamforming matrix V^(q)(k) and the quantization amplitude M_(v)(k);recovering the amplitude value r(k) according to M_(v)(k); zooming tothe real part and the imaginary part of every element in V^(q)(k)according to r(k), to recover the beamforming matrix {tilde over (v)}(k)of the subcarrier.

Another aspect of the present disclosure further provides an apparatusfor transmitting beamforming matrix, comprising: a first operationmodule, configured to calculate the maximum value m_(v)(k) of the realpart and imaginary part of the elements in subcarrier's beamformingmatrix; a first quantization module, configured to carry out a M bitsquantization to m_(v)(k) and obtain the quantization amplitude M_(v)(k);a second operation module, configured to calculate the linear part M_(v)^(lin)(k) of M_(v)(k); a second quantization module, configured to carryout a respectively N^(b) bits quantization to the real part andimaginary part of every element in V(k) by M_(v) ^(lin)(k), and obtainthe quantized beamforming matrix V^(q)(k); N^(b) is positive integer;and a transmitting module, configured to transmit said quantizationamplitude M_(v)(k) and said quantized beamforming matrix V^(q)(k).

Another aspect of the present disclosure further provides an apparatusfor receiving beamforming matrix, comprising: a receiving module,configured to receive quantized beamforming matrix V^(q)(k) of thesubcarrier, which has been quantized by the above quantization methodand transmitted, and the quantization amplitude M_(v)(k); a firstprocessing module, configured to recover the amplitude value r(k)according to M_(v)(k); a second processing module, configured to zoom tothe real part and the imaginary part of every element in V^(q)(k)according to r(k), to recover the beamforming matrix {tilde over (V)}(k)of the subcarriers.

The present disclosure provides a method and apparatus for transmittingand receiving beamforming matrix, and provides a new beamforming matrixquantization feedback scheme. Embodiments consistent with the presentdisclosure ensure the performance of quantitative feedback, reduce thealgorithm complexity and feedback overhead.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is the flowchart of the method for quantized feedback of thebeamforming matrix defined in 802.11;

FIG. 2 is the flowchart of the method for transmitting the beamformingmatrix in the first embodiment of the present disclosure;

FIG. 3 is the flowchart of the method for receiving the beamformingmatrix in the first embodiment of the present disclosure;

FIG. 4 illustrates the SNR comparison result of between the method forthe quantized feedback of the beamforming matrix in the first embodimentof the present disclosure and the method for quantized feedback of thebeamforming matrix defined in 802.11 on channel D, the bandwidth ofwhich is 20 MHz;

FIG. 5 illustrates the SNR comparison result of the above two after theadjustment of N^(b)=6 on the basis of FIG. 4;

FIG. 6 illustrates the SNR comparison result with the same quantizationparameters as FIG. 5 on channel E;

FIG. 7 illustrates the SNR comparison result of the above two after theadjustment of a=14.42, b=2 on the basis of FIG. 4;

FIG. 8 illustrates the apparatus for transmitting the beamforming matrixin the embodiment of the present disclosure; and

FIG. 9 illustrates the apparatus for receiving the beamforming matrix inthe embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

The description below and accompanying drawings fully illustratespecific embodiments of the invention, to enable one skilled in the artto implement the embodiments. Modifications, such as structural,logical, electrical and process modifications, can be made in otherembodiments. The embodiments only represent some possible variations.Individual components or functions are optional and the operation orderis variable, unless it is otherwise stated specifically. A part of and acertain feature of some embodiments may be included in or replaced by apart of and a certain feature of other embodiment. The scope of theembodiment of the invention includes the whole scope of the claims andall obtainable equivalents thereof. Herein, these embodiments of theinvention may be individually or generally represented by the term“invention” for the sake of convenience; moreover, if more than oneinvention is disclosed actually, it is not intended certainly to limitthe application scope to any individual invention or inventive concept.

The First Embodiment

After research and experimentation, an embodiment consistent with thepresent disclosure provides a new method for quantized feedback of thebeamforming matrix. Below the embodiment is described in details fromthe transmitting side and the receiving side.

FIG. 2 illustrates a method for transmitting the beamforming matrix inthe first embodiment of the prevent disclosure. The method includes thefollowing steps.

Step S201: calculating the maximum value m_(v)(k) of the real part andthe imaginary part of the elements in subcarrier's beamforming matrix.Specifically, it could be achieved by the following equation:

$\begin{matrix}{{m_{v}(k)} = {\max\begin{Bmatrix}{{\max\{ {{{Re}( {v_{({m,l})}(k)} )}}_{{m = 1},{l = 1}}^{{m = N_{r}},{l = N_{c}}} \}},} \\{\max\{ {{{Im}( {v_{({m,l})}(k)} )}}_{{m = 1},{l = 1}}^{{m = N_{r}},{l = N_{c}}} \}}\end{Bmatrix}}} & (8)\end{matrix}$wherein v_((m,l))(k) represents the element in v(k), Re(v_((m,l))(k))represents the real part of v_((m,l))(k), Im(v_((m,l))(k)) representsthe imaginary part of v_((m,l))(k); m is the row position reference, lis the column position reference, N_(r) is the maximum row number, N_(c)is the maximum column number, 1≦m≦N_(r), 1≦l≦N_(c), N_(r)≧1, N_(c)≧1, m,l, N_(r) and N_(c) are all positive integer, k is the subcarrier'sposition reference, Specifically formed as number.

V(k), of which the row number is N_(r), and the column number is N_(c),is obtained after the user site's carrying out the channel estimationbased on the feedback request of the beamforming matrix, and the SVDdecomposition to the obtained channel state information matrix (alsocalled H-matrix). N_(r) is equal to the number of transmit antennas ofthe access point (AP), and is obtained by the user site in the processof consultation of the capacity with the access point; N_(c) is equal tothe number of spatial streams, it could be set by STA as required,generally the number of spatial streams is less than the minimum valueof the number of the transmit antennas of CAP and the number of receiveantennas of STA.

Step S202: carrying out an M bits quantization to m_(v)(k) to obtain thequantization amplitude M_(v)(k). Specifically, it could be achieved bythe following equation:M _(v)(k)=min{2^(M)−1,ƒ(g(m _(v)(k)))}  (9);wherein ƒ(g(m_(v)(k))) is the function, which maps the linear m_(v)(k)to the logarithmic interval. ƒ(g(m_(v)(k))) represents the integralfunction of the result of g(m_(v)(k)). Said integral function could berounding up (represented by “└ ┘”), rounding down (represented by “┌ ┐”)or the rounding operation.

M_(v)(k) is configured to obtain the minimum value of (2^(M)−1) andƒ(g(m_(v)(k))), thus to limit the quantized result, to ensure theaccuracy of the quantization. M represents the quantization bit number,which is positive integer. Wherein, M could be a positive integergreater than or equal to 2. Considering the performance and cost,optionally, in an embodiment of the disclosure M=3 is selected.

Optionally, g(m_(v)(k))=max(0, a·log_(b)(m_(v)(k)+c)) is employed,wherein, a, b, c are all positive real number. Optionally, a=14.42, b=2,c=0.45 is selected, thus to obtain better performance of thequantization feedback of the beamforming matrix. Optionally, a=47.9,b=10, c=0.45 is selected, which could also obtain better performance ofthe quantization feedback of the beamforming matrix.

Step S203: calculating the linear part M_(v) ^(lin)(k) of M_(v)(k).Specifically, it could be achieved by the following equation:M _(v) ^(lin)(k)=b ^(M) ^(v) ^((k)/a)  (10)

Step S204: carrying out a respectively N_(b) bits quantization to thereal part and imaginary part of every element in V(k) by M_(v)^(lin)(k). Specifically, it could be achieved by the following equation:

$\begin{matrix}{{V_{({m,l})}^{q{(R)}} = {{{sign}( {V_{({m,l})}(k)} )}*{\min( {{2^{N_{b} - 1} - 1},{{round}( {\frac{{{Re}( {V_{({m,l})}(k)} )}}{{M_{v}^{lin}(k)} - c}( {2^{N_{b} - 1} - 1} )} )}} )}}}{{V_{({m,l})}^{q{(I)}} = {{{sign}( {V_{({m,l})}(k)} )}*{\min( {{2^{N_{b} - 1} - 1},{{round}( {\frac{{{Im}( {V_{({m,l})}(k)} )}}{{M_{v}^{lin}(k)} - c}( {2^{N_{b} - 1} - 1} )} )}} )}}};}} & (11)\end{matrix}$wherein, v_((m,l))(k) represents the element in v(k), V_((m,l)) ^(q(R))represents the real part of quantized v_((m,l))(k), V_((m,l)) ^(q(l))represents the imaginary part of quantized v_((m,l))(k); m is the rowposition reference, l is the column position reference,sign(V_((m,l))(k)) represents the polarity symbols of V_((m,l))(k);

$\min( {{2^{N_{b} - 1} - 1},{{round}( {\frac{{{Re}( {V_{({m,l})}(k)} )}}{{M_{v}^{lin}(k)} - c}( {2^{N_{b} - 1} - 1} )} )}} )$represents the minimum value of (2^(N) ^(b) ⁻¹−1) and

${{round}( {\frac{{{Re}( {V_{({m,l})}(k)} )}}{{M_{v}^{lin}(k)} - c}( {2^{N_{b} - 1} - 1} )} )};$round represents the rounding operation; “| |” represents the absoluteoperation; N^(b) is positive integer.

By obtaining the minimum value of (2^(N) ^(b) ⁻¹−1) and

${{round}( {\frac{{{Re}( {V_{({m,l})}(k)} )}}{{M_{v}^{lin}(k)} - c}( {2^{N_{b} - 1} - 1} )} )},$the amplitude of the quantized result is limited, to ensure the accuracyof the quantization. Considering the absolute operation is carried outduring the quantization, the recovering of the symbols' polarity (whichis the symbol's positive sign or negative sign) is needed, which is tomultiple sign(V_((m,l))(k)).

N^(b) is calculated by the user site based on the quantized overhead,which is calculated by the resource allocation information and feedbackMCS level carried in the feedback request of the beamforming matrix.N_(b) is a positive integer, and some optional values are providedhereinafter: 4, 5, 6, 8, 10, 12, which could be selected based ondifferent requirements of the quantization accuracy specifically.

Step S205: transmitting M_(v)(k) the quantized beamforming matrixV^(q)(k). Optionally, when feeding back the beamforming matrix, thetransmitter could take the subcarrier set, which needs the quantizedfeedback, as unit, and transmit together the quantized beamformingmatrix and M_(v)(k) of the subcarriers in said set. Said subcarrier set,which need the quantized feedback, is indicated when the access pointinitiates a feedback request of the beamforming matrix.

Accordingly, another embodiment of the present disclosure furtherprovides a method for receiving the beamforming matrix, recovers thebeamforming matrix by carrying out a reverse process to the quantizedbeamforming matrix V^(q)(k), illustrated in FIG. 3, comprising thefollowing steps.

Step S301: receiving the quantization amplitude M_(v)(k) and quantizedsubcarrier's beamforming matrix V^(q)(k).

Step S302: recovering the amplitude value r(k) according to M_(v)(k).Specifically, carrying out a reverse process based on the method forquantizing M_(v)(k), and recovering r(k). For example, when M_(v)(k) isquantizing by M_(v)(k)=min{2^(M)−1,ƒ(g(m_(v)(k)))}, it could employ thefollowing equation to calculate r(k):r(k)=g ⁻¹(M _(v)(k))=b ^(M) ^(v) ^((k)/a) −c  (12)wherein, g⁻¹(M_(v)(k)) is the inverse function of g(m_(v)(k)); a, b, care all positive real numbers; g(m_(v)(k)) and its inverse functiong⁻¹(M_(v)(k)) are pre-negotiated by the transmitter and receiver, andstored in the local respectively.

Step S303: zooming to the real part V_((m,l)) ^(q(R))(k) and theimaginary part v_((m,l)) ^(q(I))(k) of every element v_((m,l)) ^(q)(k)in V^(q) (k) according to r(k), to recover the beamforming matrix {tildeover (v)}(k) of said subcarrier. Specially, it could be achieved by thefollowing equation:

$\begin{matrix}{{{{Re}( {{\overset{\sim}{V}}_{({m,l})}(k)} )} = \frac{{r(k)}{V_{({m,l})}^{q{(R)}}(k)}}{( {2^{N_{b} - 1} - 1} )}}{{{Im}( {{\overset{\sim}{V}}_{({m,l})}(k)} )} = \frac{{r(k)}{V_{({m,l})}^{q{(I)}}(k)}}{( {2^{N_{b} - 1} - 1} )}}} & (13)\end{matrix}$

We found the following after comparing the first embodiment of thedisclosure and the scheme of 802.11.

Regarding the complexity of the algorithm realization: in contrast tothe calculation of M_(v)(k) and its linear value both need the divisionto m_(v)(k) in the scheme of 802.11, the technical solution in thepresent disclosure has low algorithm complexity and less computation.

Regarding the feedback overhead: according to the feedback codingprocess (S201˜S205) of the beamforming matrix of the above transmitterin the prevent disclosure, it shows that, the feedback overhead neededin the mode of quantized feedback of the beamforming matrix is the sumof the needed bit number of M_(v)(k) and quantized beamforming matrixV^(q)(k): M+2×N_(b)×N_(r)×N_(c), the overhead is N_(Alpha) less than thescheme defined in 802.11. Referred to table 1 specifically, comparingthe feedback overhead between the scheme of 802.11 and the scheme of thefirst embodiment in the present disclosure, as both of them carry outthe quantization to the real part and the imaginary part, they use thesame quantization bit number Nb, however, the scheme of the firstembodiment doesn't need to feedback the value of Alpha. Therefore, thefirst embodiment of the present disclosure costs less feedback overhead.

a. Table 1 feedback overhead i. feedback overhead IEEE B_(feedback) =N_(feedback) (scaleB + N_(tx)N_(rx) (realB + imagB) + 802.11n N_(Alpha))scaleB = M (bits) realB = imagB = N_(b) (bits) first B_(feedback) =N_(feedback) · (scaleB + N_(tx)N_(rx) (realB + imagB)) embodiment scaleB= M (bits) in the realB = imagB = N_(b) (bits) present disclosurewherein, B_(feedback) is the feedback overhead, N_(feedback) is thenumber of the elements in the feedback subcarrier set Ω_(feedback),scaleB is the quantization bit of M_(H)(k), N_(tx) is the number of CAPtransmit antennas, N_(rx), is the number of STA receive antennas, realBis the quantization accuracy of the real part; imagB is the quantizationaccuracy of the imaginary part.

On the feedback performance, the first embodiment in the presentdisclosure first selects M_(v)(k)=min{2^(M)−1,round(47.9·lg(m_(v)(k)+0.45)}, a=47.9, b=10, c=0.45, N_(b)=8, M=3,comparing the quantization SNR of the quantization algorithm of thebeamforming matrix provided by the first embodiment in the presentdisclosure and IEEE802.11, the result of their quantization SNR whenboth of them are on channel D, the bandwidth of which is 20 MHz, isillustrated in FIG. 4, as seen from the figure, both of them have thesame or similar performance.

Adjust the value of the parameter N_(b) in the scheme of the firstembodiment in the present disclosure, while keeping the other parametersthe same; select M_(v)(k)=min{2^(M)−1, round (47.9·lg(m_(v)(k)+0.45)},a=47.9, b=10, c=0.45, N_(b)=6, M=3, when both of them are on 20 MHzchannel B the comparing result is illustrated in FIG. 5, as seen fromthe figure, both of them still have the same or similar performance.Keep the parameters unchanged, which is, selectM_(v)(k)=min{2^(M)−1,round(47.9·lg(m_(v)(k)+0.45)}, a=47.9, b=10,c=0.45, N_(b)=6, M=3, check the comparing result when they are on the 20MHz channel E, as illustrated in FIG. 6, both of them still keep thesame or similar performance.

Continue to adjust the value of the parameter a, b of the scheme of thefirst embodiment in the present disclosure, selectM_(v)(k)=min{2^(M)−1,round(14.42·log₂(m_(v)(k)+0.45)}, a=14.42, b=2,c=0.45, N_(b)=8, M=3, the comparing result when they are both on the 20MHz channel D is illustrated in FIG. 7. As shown in FIG. 7, both of themstill keep the same or similar performance.

After the recovery of {tilde over (v)}(k), the receiver could calculatethe subcarrier's precoding matrix Q_(k) according to {tilde over(v)}(k). Because the performance of the recovery of {tilde over (v)}(k)in the above scheme of the first embodiment in the present disclosureand IEEE802.11 is similar, therefore, Q_(k) could be obtained in highaccuracy.

Another embodiment in the present invention provides an apparatus fortransmitting the beamforming matrix, as illustrated in FIG. 8, includethe following components. A first operation module 801, configured tocalculate the maximum value m_(v)(k) of the real part and imaginary partof the elements in subcarrier's beamforming matrix. A first quantizationmodule 802, configured to carry out an M bits quantization to m_(v)(k)and obtain the quantization amplitude M_(v)(k). A second operationmodule 803, configured to calculate the linear part M_(v) ^(lin)(k) ofM_(v)(k). A second quantization module 804, configured to carry out arespectively N_(b) bits quantization to the real part and imaginary partof every element in V(k) by M_(v) ^(lin)(k), and obtain the quantizedbeamforming matrix V^(q)(k); N_(b) is positive integer. A transmittingmodule 805, configured to transmit said quantization amplitude M_(v)(k)and said quantized beamforming matrix V^(q)(k).

Optionally, said first quantization module 802, configured to carry outa M bits quantization to m_(H)(k) according toM_(v)(k)=min{2^(M)−1,ƒ(g(m_(v)(k)))}; wherein, M_(v)(k) is configured toobtain the minimum value of (2^(M)−1) and ƒ(g(m_(v)(k))); the functionƒ(g(m_(v)(k))) represents the integral function of the result ofg(m_(v)(k)); g(m_(v)(k)) is configured to map the linear m_(v)(k) to theinterval which is represented from natural number to logarithm, M ispositive integer.

Optionally, g(m_(v)(k))=a·log_(b)(m_(v)(k)+c), a, b, c are all positivereal numbers.

Optionally, said second operation module 803 calculates the linear partM_(v) ^(lin)(k) of M_(v)(k) according to the equation M_(v)^(lin)(k)=b^(M) ^(v) ^((k)/a).

Optionally, said integer operation could be rounding up, rounding downor the rounding operation.

Optionally, M is greater than or equal to 2.

Optionally, M could be equal to 3.

Optionally, a=14.42, b=2, c=0.45 could be selected.

Optionally, a=47.9, b=10, c=0.45 could be selected.

Optionally, said second quantization module 804, it could be achieved bythe following equation:

$V_{({m,l})}^{q{(R)}} = {{{{{sign}( {V_{({m,l})}(k)} )}*{\min( {{2^{N_{b} - 1} - 1},{{round}( {\frac{{{Re}( {V_{({m,l})}(k)} )}}{{M_{v}^{lin}(k)} - c}( {2^{N_{b} - 1} - 1} )} )}} )}}:V_{({m,l})}^{q{(I)}}} = {{{{sign}( {V_{({m,l})}(k)} )}*{\min( {{2^{N_{b} - 1} - 1},{{round}( {\frac{{{Im}( {V_{({m,l})}(k)} )}}{{M_{v}^{lin}(k)} - c}( {2^{N_{b} - 1} - 1} )} )}} )}}:}}$

Carrying out a respectively N_(b) bits quantization to the real part andthe imaginary part of each element in V(k); V_((m,l))(k) represents theelement in V(k), V_((m,l)) ^(q(R)) represents the real part of quantizedV_((m,l))(k), V_((m,l)) ^(q(I)) represents the imaginary part ofquantized V_((m,l))(k); m is the row position reference, l is the columnposition reference, sign(V_((m,l))(k)) represents the polarity symbolsof V_((m,l))(k);

$\min( {{2^{N_{b} - 1} - 1},{{round}( {\frac{{{Re}( {V_{({m,l})}(k)} )}}{{M_{v}^{lin}(k)} - c}( {2^{N_{b} - 1} - 1} )} )}} )$represents the minimum of (2^(N) ^(b) ⁻¹−1) and

${{round}( {\frac{{{Re}( {V_{({m,l})}(k)} )}}{{M_{v}^{lin}(k)} - c}( {2^{N_{b} - 1} - 1} )} )};$round represents the rounding operation; “| |” represents the absoluteoperation; N_(b) is positive integer.

Optionally, the value of N_(b) could be one of 4, 5, 6, 8, 10, 12.

Optionally, said transmitting module 805, is configured to transmittogether the quantization amplitude M_(v)(k) of each subcarrier in theset of the subcarriers, which need the feedback and the quantized Vmatrix.

Another embodiment in the present disclosure provides an apparatus forreceiving the beamforming matrix, as illustrated in FIG. 9, includingthe following components. A receiving module 901, configured to receivequantized beamforming matrix V_(q)(k) of the subcarrier, which has beenquantized by the above quantization method and transmitted, and thequantization amplitude M_(v)(k). A first processing module 902,configured to recover the amplitude value r(k) according to M_(v)(k). Asecond processing module 903, configured to zoom to the real part andthe imaginary part of every element in V^(q)(k) according to r(k), torecover the beamforming matrix {tilde over (V)}(k) of the subcarriers.Optionally, said first processing module 902, configured to carry out areverse process based on the method of quantizing M_(v)(k), and recoverthe amplitude value r(k).

For example, when is M_(v)(k) quantizing by employingM_(v)(k)=min{2^(M)−1,ƒ(g(m_(v)(k)))}, the following equation (12) couldbe employed to calculate r(k).

Optionally, said second processing module 903, is configured to zoom thereal part and the imaginary part of every element in v^(q)(k) accordingto

${{Re}( {{\overset{\sim}{V}}_{({m,l})}(k)} )} = \frac{{r(k)}{V_{({m,l})}^{q{(R)}}(k)}}{( {2^{N_{b} - 1} - 1} )}$${{{Im}( {{\overset{\sim}{V}}_{({m,l})}(k)} )} = \frac{{r(k)}{V_{({m,l})}^{q{(I)}}(k)}}{( {2^{N_{b} - 1} - 1} )}};$wherein, {tilde over (v)}_((m,l))(k) represents the element in {tildeover (v)}(k), Re({tilde over (v)}_((m,l))(k)) represents the real partof quantized {tilde over (v)}_((m,l))(k), Im({tilde over(v)}_((m,l))(k)) represents the imaginary part of quantized {tilde over(v)}_((m,l))(k); V_((m,l)) ^(q)(k) represents the element in V^(q)(k);V_((m,l)) ^(q(R))(k) represents the real part of V_((m,l)) ^(q)(k);V_((m,l)) ^(q(I))(k) represents the imaginary part of V_((m,l)) ^(q)(k);m is the row position reference, l is the column position reference, thequantization bit N_(b) is positive integer.

Optionally, said apparatus for receiving the beamforming matrix couldcomprise an operation module 904, configured to calculate thesubcarrier's precoding matrix Q_(k) according to {tilde over (v)}(k).

Other embodiments of the disclosure will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the claims.

What is claimed is:
 1. A method for transmitting a beamforming matrix ofa subcarrier on a channel of a Multiple Input Multiple Output (MIMO)channel of a MIMO system by a transmitter in response to a feedbackrequest from a receiver for obtaining channel information in the MIMOsystem, comprising: determining, by the transmitter, a maximum valuem_(v)(k) of a real part and an imaginary part of elements in asubcarrier's beamforming matrix V(k); determining, by the transmitter,an M bits quantization of m_(v)(k); determining, by the transmitter, aquantization amplitude M_(v)(k), M being a positive integer, wherein nodivision calculation is performed on m_(v)(k) to determine M_(v)(k);determining, by the transmitter, a linear part M_(v) ^(lin)(k) ofM_(v)(k), wherein no division calculation is performed on m_(v)(k) todetermine the linear part M_(v) ^(lin)(k) of M_(v)(k); determining, bythe transmitter, a N_(b) bits quantization of a real part and imaginarypart of every element in V(k) by M_(v) ^(lin)(k); determining, by thetransmitter, a quantized beamforming matrix V^(q)(k), N_(b) being apositive integer, wherein${V_{({m,l})}^{q{(R)}} = {{{sign}( {V_{({m,l})}(k)} )}*{\min( {{2^{N_{b} - 1} - 1},{{round}( {\frac{{{Re}( {V_{({m,l})}(k)} )}}{{M_{v}^{lin}(k)} - c}( {2^{N_{b} - 1} - 1} )} )}} )}}};$${V_{({m,l})}^{q{(I)}} = {{{sign}( {V_{({m,l})}(k)} )}*{\min( {{2^{N_{b} - 1} - 1},{{round}( {\frac{{{Im}( {V_{({m,l})}(k)} )}}{{M_{v}^{lin}(k)} - c}( {2^{N_{b} - 1} - 1} )} )}} )}}};$V_((m,l))(k) representing an element in V(k); V_((m,l)) ^(q(R))representing a real part of quantized V_((m,l))(k); V_((m,l)) ^(q(I))representing an imaginary part of quantized V_((m,l))(k); m being a rowposition reference, l being a column position reference;sign(V_((m,l))(k)) representing a polarity symbols of V_((m,l))(k);min(2^(N) ^(b) ⁻¹−1,$ {{round}( {\frac{{{Re}( {V_{({m,l})}(k)} )}}{{M_{v}^{lin}(k)} - c}( {2^{N_{b} - 1} - 1} )} )} )$representing a minimum value of (2^(N) ^(b) ⁻¹−1) and${{round}( {\frac{{{Re}( {V_{({m,l})}(k)} )}}{{M_{v}^{lin}(k)} - c}( {2^{N_{b} - 1} - 1} )} )};$round representing a rounding operation; “| |” representing an absoluteoperation; and c being a positive real number; and transmitting, by thetransmitter, said quantization amplitude M_(v)(k) and said quantizedbeamforming matrix V^(q)(k).
 2. The method of claim 1, wherein the Mbits quantization of m_(v)(k) is determined as follows:M _(v)(k)=min{2^(M)−1,ƒ(g(m _(v)(k)))}; M_(v)(k) being a minimum valueof (2^(M)−1) and ƒ(g(m_(v)(k))); ƒ(g(m_(v)(k))) representing an integralfunction of a result of g(m_(v)(k)); g(m_(v)(k)) mapping a linearm_(v)(k) from an interval of natural numbers to an interval oflogarithmic numbers, M being a positive integer.
 3. The method of claim2, wherein g(

_(v)(k))=a lo

_(b)(m_(v)(k)c), a, b, c being positive real numbers.
 4. The method ofclaim 3, wherein the linear part M_(v) ^(lin)(k) of M_(v)(k) isdetermined by an equation: M_(v) ^(lin)(k)=b^(M) ^(v) ^((k)/a).
 5. Themethod of claim 3, wherein a equals to 14.42, b equals 2, c equals to0.45; or a equals to 47.9, b equals to 10, c equals to 0.45.
 6. Themethod of claim 1, wherein M is greater than
 1. 7. The method of claim6, wherein M is equal to
 3. 8. The method of claim 1, wherein the valueof N_(b) is one of 4, 5, 6, 8, 10, or
 12. 9. The method of claim 1,further comprising: transmitting said quantization amplitude M_(v)(k) ofeach subcarrier in a set of subcarriers and said quantized beamformingmatrix V^(q)(k) together.
 10. A method for a receiver receiving abeamforming matrix of a subcarrier on a Multiple Input Multiple Output(MIMO) channel of a MIMO system from a transmitter to obtain channelinformation in the MIMO system when the receiver initiates a feedbackrequest, comprising: receiving, by the receiver, a quantizedsubcarrier's beamforming matrix V^(q)(k) and a quantization amplitudeM_(v)(k), wherein${V_{({m,l})}^{q{(R)}} = {{{sign}( {V_{({m,l})}(k)} )}*{\min( {{2^{N_{b} - 1} - 1},{{round}( {\frac{{{Re}( {V_{({m,l})}(k)} )}}{{M_{v}^{lin}(k)} - c}( {2^{N_{b} - 1} - 1} )} )}} )}}};$${V_{({m,l})}^{q{(I)}} = {{{sign}( {V_{({m,l})}(k)} )}*{\min( {{2^{N_{b} - 1} - 1},{{round}( {\frac{{{Im}( {V_{({m,l})}(k)} )}}{{M_{v}^{lin}(k)} - c}( {2^{N_{b} - 1} - 1} )} )}} )}}};$V_((m,l))(k) representing an element in V(k); V_((m,l)) ^(q(R))representing a real part of quantized V_((m,l))(k); V_((m,l)) ^(q(I))representing an imaginary part of quantized V_((m,l))(k); m being a rowposition reference, l being a column position reference;sign(V_((m,l))(k)) representing a polarity symbols of V_((m,l))(k);$\min( {{2^{N_{b} - 1} - 1},{{round}( {\frac{{{Re}( {V_{({m,l})}(k)} )}}{{M_{v}^{lin}(k)} - c}( {2^{N_{b} - 1} - 1} )} )}} )$representing a minimum value of (2^(N) ^(b) ⁻¹−1) and${{round}( {\frac{{{Re}( {V_{({m,l})}(k)} )}}{{M_{v}^{lin}(k)} - c}( {2^{N_{b} - 1} - 1} )} )};$ round representing a rounding operation; “| |” representing an absoluteoperation; N_(b) being a positive integer and c being a positive realnumber; recovering, by the receiver, an amplitude value r(k) accordingto M_(v)(k), including carrying out a reverse process based on a methodfor quantizing M_(v)(k), wherein no division calculation is performed onm_(v)(k) for quantizing M_(v)(k); scaling, by the receiver, a real partand an imaginary part of every element in V^(q)(k) according to r(k);recovering, by the receiver, a beamforming matrix {tilde over (v)}(k) ofa subcarrier; and calculating, by the receiver, the subcarrier'sprecoding matrix Q_(k) according to {tilde over (V)}(k).